CV Beta Blockers

Question 1

What are the common indications for Beta Blockers?

Answer 1

1. Ischaemic heart disease: as a first-line option to improve symptoms and prognosis associated with angina and acute coronary syndrome.
2. Chronic heart failure: as a first-line option to improve prognosis.
3. Atrial fibrillation: as a first-line option to reduce the ventricular rate and, in paroxysmal atrial fibrillation, to maintain sinus rhythm.
4. Supraventricular tachycardia (SVT): as a first-line option in patients without circulatory compromise to restore sinus rhythm.
5. Hypertension: although not generally indicated for initial therapy, they may be used when other medicines (e.g. calcium channel blockers, ACE inhibitors, thiazide diuretics) are insufficient or inappropriate.

Question 2

Mechanism of Action?

Answer 2

1. B1 receptors in heart
2. B2 receptors in smooth muscles of blood vessels
3. Via B1: reduce force of contraction of heart
4. Slow VR: by prolonging refractory period of AV node
5. B blockers break re-entry circuit
6. In hypertension B blockers reduce BP via number of mechanisms, one of which is to reduce renin.

Question 3

Adverse effects?

Answer 3

Beta-blockers commonly cause fatigue, cold extremities, headache and gastrointestinal disturbance (e.g. nausea). They can cause sleep disturbance and nightmares. They may cause impotence in men.

Question 4

Warnings?

Answer 4

1. Patients with astma can cause bronchospasm
2. Choose B1 selective B blockers: atenolol, bisoprolol, metoprolol
3. Not propanolol

Question 5

Important interactions?

Answer 5

Beta-blockers must not be used with non-dihydropyridine calcium channel blockers (e.g. verapamil, diltiazem). This combination can cause heart failure, bradycardia, and even asystole.

Question 6

Clinical Tip?

Answer 6

1. For ACS usually best to select drugwith short half life
2. EG standard release metaprolol
3. More responsive to dose adjustment
4. Can then be converted to once daily bisoprolol